Caching Decorator (decorated-cache)

This module provides a simple, customizable caching solution for methods in TypeScript classes. By utilizing a Map to store and retrieve cached results and using the sha256 hashing algorithm for key generation, it offers a balance between performance and collision resistance.

Overview

The cached function is a decorator factory that wraps around class methods to memoize their results based on the arguments passed to them. It supports three modes of operation for generating cache keys:

raw: Uses a JSON string representation of the method arguments.
multi-sha256: Generates a SHA-256 hash for each argument individually, then concatenates these hashes.
single-sha256: Generates a single SHA-256 hash based on the JSON string representation of all arguments.

By default, it uses the raw mode if no specific key generation strategy is provided.

Installation

To use this module, ensure you have Node.js installed, as it requires the crypto module for generating SHA-256 hashes.

Usage

First, import the decorator:

import cached from 'path/to/file';

Then, apply it to class methods you wish to cache. You can customize the caching behavior by specifying the key generation strategy ('raw', 'multi-sha256', or 'single-sha256') and providing an existing Map object as a cache store.

Basic Example (Using Defaults)

class Calculator {
  @cached()
  add(a, b) {
    return a + b;
  }
}

Advanced Example (Custom Configuration)

const globalCache = new Map();

class AdvancedCalculator {
  @cached('multi-sha256', globalCache)
  complexOperation(a, b) {
    // Simulate a CPU-intensive task
    return a * b + Math.sqrt(a + b);
  }
}

A Working Example

class Fibonacci {
    @cached()
    cached(n: number): number {
        if (n < 2) {
            return 1;
        }
        return this.cached(n - 2) + this.cached(n - 1);
    }

    @cached('multi-sha256')
    cachedMultiSha256(n: number): number {
        if (n < 2) {
            return 1;
        }
        return this.cachedMultiSha256(n - 2) + this.cachedMultiSha256(n - 1);
    }

    uncached(n: number): number {
        if (n < 2) {
            return 1;
        }
        return this.uncached(n - 2) + this.uncached(n - 1);
    }
}

let fib = new Fibonacci();

console.log('Started');

function test(func: () => number) {
    let start = Date.now();
    let result = func();
    let end = Date.now();
    console.log(`result: ${result}, time: ${end - start}ms`);
}

test(() => fib.cached(40));
test(() => fib.cachedMultiSha256(40));
test(() => fib.uncached(40));

Parameters

key: An optional parameter to specify the cache key generation strategy. Acceptable values are 'raw', 'multi-sha256', or 'single-sha256'. The default is 'raw'.
cacheParent: An optional Map object to serve as the cache store. If not provided, a new Map will be instantiated.

How It Works

When a decorated method is called, the decorator generates a cache key based on the method's arguments and the specified strategy. If the cache contains a value for that key, the cached value is returned immediately, bypassing the original method. Otherwise, the original method is invoked, and its result is cached before being returned.

Considerations

Performance: While caching can significantly improve performance for computationally intensive operations or I/O-bound tasks, the overhead of key generation (especially when using SHA-256 hashing) may influence the overall benefits. Choose the key generation strategy that best fits your use case.
Collision Resistance: The single-sha256 strategy offers strong collision resistance at the cost of computational overhead. In contrast, the raw method may be faster but is susceptible to collisions if complex objects are involved.
Cache Invalidation: This implementation does not provide built-in cache invalidation or expiration mechanisms. It is up to the developer to manage the lifecycle of cached data.

License

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

wraith4081/decorated-cache